A high speed, manually powered tool allows for relatively high speed driving, while the operator maintains direct control over the axial force, torque, and turning rate applied to the driven element. In contrast, motorized drivers provide poor control of the rotation speed and torque applied to the driven element. The operator controls a switch, which in turn controls a motor, which finally powers the driven element. The user, accordingly, has little direct control over the events occurring at the driven element. In many instances, this lack of “feel” by the operator causes damage to the driven element and/or to its surroundings, especially in medium and light duty applications.
As disclosed in U.S. Pat. Nos. 4,524,650 and 4,739,838 to the present inventor, a squeeze tool serves to convert squeezing motion into rotary motion on a variable torque basis, and serves to transmit the rotary motion to a screw, bolt, or other fastener, which is being tightened or loosened. The tool incorporates a pull lever and a varying force transmitting lever which operate in conjunction with a squeeze handle to provide a traveling fulcrum, so that when the squeeze handle is squeezed, maximum torque and minimum speed are generated at the beginning of the stroke, and maximum speed and minimum torque are realized for the remainder of the stroke. However, these prior designs are not compact, require many components, have limited torque to failure, and are unnecessarily expensive to produce. Further, the action required to change rotation direction is not efficient, requiring inserting a finger into the internals of the tool.
Other manual rotary tools have used gear amplification to convert squeezing action to rotary motion. However, such designs require complex structures to provide ratcheting action and reversible direction and are of limited strength.